(1) Field of the Invention
The present invention relates to an optical pickup device and an optical disc apparatus.
(2) Description of the Related Art
A technique concerned with the technical field of the present invention is described in, for example, JP-A-2006-344344, which discloses the technique as a “method of acquiring desired signals accurately from an optical disc having a plurality of recording layers”. Another related technique is disclosed in JP-A-2006-344480, which discloses the technique as a “method of detecting a tracking error signal minimized in offset level, even when a recordable optical storage medium with two information-recording surfaces is used”. Yet another related technique is described in, for example, IEICE Technical Bulletin CPM2005-149 (2005-10) that is a non-patent document (IEICE: the Institute of Electronics, Information and Communication Engineers). In CPM2005-149, the technique is introduced as a “method of disposing a tracking photodetector in a region free from any stray light leaking from other layers”, and its related apparatus configuration is described in JP-A-2004-28102 as well as in the Technical Bulletin.
JP-A-2008-102998, for example, discloses a further, related technique as a “method of constructing various regions of a dividing element and a light-receiving section of a photodetector so that when a desired information-recording layer of an optical disc is focused, only the beam of light that is reflected from the desired information-recording layer will be converged upon the surface of the light-receiving section of the photodetector and no beam reflections from other information-recording layers will strike upon the light-receiving section of the photodetector”.